The present invention relates to an attached matter detector that detects matter attached on a transparent member based on an image imaged by an imager, and an in-vehicle device controller using the attached matter detector.
Japanese Patent No. 4326999 discloses an image-processing system (attached matter detector) that detects foreign matter (attached matter) such as a liquid drop such as a raindrop, or the like, fogging, dust, and the like attached on surfaces of glasses used for a vehicle, a vessel, an airplane, and the like, or various types of window glass (transparent members) such as window glass used in a building, and so on. In this image-processing system, light is emitted to a front window of a driver's vehicle from a light source placed in an interior of the driver's vehicle, and an image sensor receives reflected light of the light emitted to the front window, and images an image. Then, the imaged image is analyzed, and whether foreign matter such as a raindrop, or the like is attached on the front window is determined. In particular, an edge detection operation is performed on an image signal of the imaged image when lighting the light source by using a Laplacian filter, or the like, and an edge image is created in which a boundary between an image region of a raindrop and an image region of a non-raindrop region is enhanced. And then, the Generalized Hough Transform is performed on the edge image, round-shape image regions are detected, the number of detected round-shapes is counted, the number of the detected round-shapes is converted to an amount of rain, and the amount of rain is calculated.
In Japanese Patent Application No. 2011-240848 (Hereinafter, referred to as “prior application”), the applicant of the present invention proposed an imaging unit that images an image in which a front region of a driver's vehicle is taken as an imaging region via a front window, and images an image of a raindrop attached on an outer surface of the front window. The imaging unit according to the prior application will be explained with reference to the drawings below.
FIG. 25A is an explanatory diagram illustrating a light path of light that is emitted from a light source 202, reflected by a raindrop 203, and incident to an imaging device 200. FIG. 25B is an explanatory diagram illustrating an example of an image of imaged image data.
The imaging unit of the prior application includes the imaging device 200, and the light source 202, and is placed on a side of an inner surface of a front window 105 of the driver's vehicle. As to the imaging device 200, so as to image a predetermined imaging region (a front region of the vehicle), an angle is adjusted such that an imaging direction (an optical axis direction of an imaging lens) P of the imaging device 200 faces a specified direction. Therefore, as illustrated in FIG. 25B, the front region of the vehicle is appropriately shown in an image region for vehicle detection 213.
On the other hand, as illustrated in FIG. 25A, as to the light source 202, an angle is adjusted such that light emitted from the light source is reflected by the raindrop 203 (specifically, an interfacial surface between the raindrop 203 and air) attached on an outer surface of the front window 105, and the reflected light is shown in an image region for attached matter detection 214. Therefore, as illustrated in FIG. 25B, an image of the raindrop 203 attached on the outer surface of the front window 105 is appropriately shown in the image region for the attached matter detection 214.
In order to improve detection accuracy of attached matter, it is important to prevent light different from the light emitted from the light source 202 (ambient light) from being incident to the image region for the attached matter detection 214. Therefore, as to the imaging unit of the prior application, an image of the image region for the attached matter detection 214 is imaged via a spectral filter that transmits a wavelength range (for example, an infrared light region) of the light emitted from the light source 202 and cuts a visible light region.
However, in addition to the light emitted from the light source 202, light of the same wavelength (ambient light) as the wavelength of the light emitted from the light source 202 (light source wavelength) is also incident to the image region for attached matter detection 214. In particular, in a case of imaging an image of an imaging region of an external area such as the front region of the vehicle in the image region for vehicle detection 213, various types of light including sunlight are incident to the image region for attached matter detection 214, and intense ambient light having the same wavelength as the light source wavelength is incident to the image region for the attached matter detection 214. The ambient light having such a wavelength is not removed by a spectral filter that cuts a wavelength other than the light source wavelength, and causes a problem that worsens the detection accuracy of the attached matter.